The invention concerns the method of making a physically and chemically active environment by means of a plasma jet which permits the transformation and the oriented transfer of electromagnetic energy in its different forms by means of a plasma, from the plasma jet to the treated object.
For making a physically and chemically active environment utilised for the treatment of objects or chemical compounds currently a broad spectrum of discharges generated in different ways on the basis of electromagnetic energy are used which in turn affect the activated medium or directly the treated objects.
From CZ 246982 a method of spatially oriented chemical activation of the working gas by plasma is known in the region between the jet attached via the adapting member to the source of high-frequency (hf) energy with a non-symmetric output and the earthed electrode attached to the second output of the above source. The use of the method is only limited to low pressures, a gaseous working medium and an external plasmatic environment.
From PV 03925-90.J CZxe2x80x94priority Sept. 9, 1990 and WO 95/11322 modifications of the preceding mentioned method are known, characterised by the fact that the generation of the discharge activating the working gas passing through the jet takes place already inside the hollow electrode in the working regime of the so-called high-frequency hollow cathode. In WO 95/11322, as against PV 03925-90.J CZ, the in turns discharge and non-discharge operation regime is utilised for sputtering the material of the electrode, in PV 03925-90.J CZ a permanent magnet situated axially symmetrically outside the jet is used for orienting plasmochemical processes. These two methods are only limited to low pressures, a gaseous working medium and an external plasmatic environment.
According to WO 96/16531 the plasma is generated under low pressure in a gaseous working medium, by means of the so-called hf hollow cathode of linear geometry and plasmochemical processes are oriented by means of an additional magnetic field of other than axial symmetry from permanent magnets or electromagnets.
From SE 9302222-6 a modification of the preceding patents is known where the hollow electrode is fed from a microwave source.
The main drawback of the above methods and equipment for their performance is the fact that they are only limited to low pressures up to 102-3 Pa, a gaseous working medium and an external plasmatic environment.
From Jpn. J. Appl. Phys. 33 (1994), L 197, a method of generating hf plasma under atmospheric pressure is known. In this case the hf. discharge is not generated in the electrode with a hollow geometry, but on a compact needle electrode inserted into the dielectric tube flown through only by the working medium in the gaseous state. The disadvantage of this method and equipment is the fact that the discharge is generated on the fill needle electrode, by which the plasmochemical processes of activating the streaming working medium are not so much effective as in the case of the discharge in the hollow electrode. It is applicable only in a medium formed by the gaseous phase, where the oriented reaction channel is formed, capable of activating a further object or the working medium.
In Plasma Sources Sci. Technol. 6, 1997, 468-477 a method is described of generating a high-pressure discharge of the type of a direct current hollow cathode in a gas without a flow through regime. The equipment consists of two electrodes, of which the cathode has a cavity with a cylindrical symmetry with the inner diameter of about 0.2 to 0.7 mm and which is separated from the anode immediately linking up with the cathode hollow by a layer of the dielectric material. It is thus not a plasma jet because only gas is used without the flow through regime. The equipment is not used for the activation or adaptation of any further activated working medium or object and the electrodes are fed only from a direct current source.
From CZ 282566 B6 and Proc. of 18th Symp. on Plasma Phys. and Technology, Prague, 1997, 144-146, a method is known of generating a volume corona discharge in water or in water with admixtures between the electrodes to which pulse voltage is applied, characterised by the fact that the intensity of the electric field in the proximity of at least one of the electrodes increases by a partial coverage of this electrode by a solid and/or gaseous dielectric, and on the surface of the electrode spots are formed of the contact of the electrode material, the solid and/or gaseous dielectric and/or water (the so-called xe2x80x9ctriple pointsxe2x80x9d of different dielectric constants). The equipment for performing this kind consists of a big cylindrical metal reactor which is at the same time one electrode flown through slowly by the above liquid medium. The second rod-shaped electrode is placed longitudinally in the axis of that reactor. The method of generating the discharge can be carried out only in the aqueous medium. The equipment is voluminous and only works when using a very efficient pulse source of direct current electric energy (of the order of tens of MW in a pulsexe2x80x94Proc. of the 18th Symp. on Plasma Phys. and Technology, Prague, 1997, 144-146).
All these methods are closely connected with an actual and highly specific arrangement of plasma generating equipment and highly specific working conditions (working environment, medium, pressure, temperature, frequency of the excitation electromagnetic energy, power output of its source, etc.). The facilities used in practice are usually narrowly specialised, spacious and they require a closed room (e.g. vacuum facilities) or are highly requiring for energy consumption (e.g. plasmatronsxe2x80x94tens kW) or 15 for the method of discharge generation (such as a pulse coronaxe2x80x94tens of kW to MW in a pulse). Hitherto no possibility has existed of targeted, space narrowly directed, sufficiently fine, but effective, superficial or small-volume adaptations of objects under higher pressures (particularly in free atmosphere or in a liquid medium), carried out by a single facility in the whole spectrum of frequencies of the source voltage.
The above drawbacks are removed by the method of generating a physically and chemically active environment by means of the plasma jet, according to the invention consisting in the fact that from at least one external source of performance of about 100 to 103 W and voltage amplitude of the order of 101 to 104 V with the possibility of its modulation at the frequency range of DC (ss), low frequency (nf), high frequency (hf) or microwaves (vhf) electromagnetic energy is conducted to at least one hollow electrode flown through by the stream of the working medium in which an electromagnetic field is formed in the longitudinal and/or transversal direction of the electrode cavity and/or its orifice, and at the same time free carriers of the charge are generated by the action of elements locally increasing the density of electromagnetic energy and collision processes of particles in the working medium and on the surface of the hollow electrode by which, inside tee electrode cavities or/and at its orifice and in the external medium an intense discharge is generated or a system of primary and filamentary discharges with their own internal streaming which are carried by the flowing through working medium which are gradually activated and thus formed plasma, together with the streaming and henceforth activating working medium flow through the hollow electrode and in the external medium at subsonic or supersonic speed with contemporaneous generation of a pointed reaction channel at the pressure of 103 to 106 Pa.
The transfer of electromagnetic energy into the discharge carried by the working medium is matched adapted.
The working medium and the external medium is a gas, a liquid or their mixtures or a mixture of solid particles with the gas, liquid or their mixtures.
The process of plasma generation and the activation of the working medium is advantageously co-generated and controlled by another magnetic field formed from a permanent magnet and/or from an electromagnet or their system.
The plasma jet for generating a physically and chemically active environment according to the invention consists in the fact that it is formed by at least one hollow electrode of conducting or conducting and dielectric material with at least one element locally increasing the density of electromagnetic energy inside the hollow electrode and/or at its orifice and/or outside which is constituted by a construction element and/or a physical element operating in the transversal and/or longitudinal direction with respect to the streaming working medium and further it is constituted by at least one source of electromagnetic energy attached via the system of regulation, transformation and transfer elements to the conducting part of the hollow electrode.
The design element consists of the rough surface of the electrode material and/or the cavity and/or the projection and/or point and/or edge placed inside the electrode cavity and/or outside and/or in its orifice; and/or of openings and/or slits formed inside the hollow electrode and/or a contact place of the conducting part of the electrode with dielectric material.
The physical element is selected from a group consisting of the supplementary electrode of different potential than the hollow electrode and/or the source of electrically charged particles or particles excited into higher energy levels of excited particles and/or a source of photons or particles with high energies operating in the transversal and/or longitudinal direction with respect to the streaming working medium.
With an advantage a magnet and/or an electromagnet is placed inside or outside the hollow electrode.
The hollow electrode is fixed to a non-conductive holder which permits manual or mechanical handling.
In this way it is possible to make four fundamental types of highly variable and dynamic high-pressure one pole (feeding the electrode with hf energy) or dipole (source of electromagnetic energy without band limitation) discharges or systems of discharges which can link up with each other and which are blown out of the cavity of the plasma jet or walls of its orifice and directed in the external environment. These fundamental types of discharges are as follows:
1. A high-pressure discharge or a system of discharges generated inside the hollow electrode which is a constituent of the plasma jet and/or forms it, and is blown out of it or which is blown out of the walls of its orifice and/or the system of its cavities (multicellular discharge). This discharge or the system of discharges can be characterised by two limiting states:
a) The plasma is actively generated inside the electrode cavity only at the negative part of the voltage amplitude on the electrode (the hollow electrode is the cathodexe2x80x94from about the frequency of 1 kHz the plasma keeps in the electrode cavity permanently).
b) The plasma is actively generated inside the electrode cavity irrespective of the voltage amplitude on the electrode (e.g. by the above elements locally increasing the density of electromagnetic energy).
1. A high-pressure xe2x80x9caggravatedxe2x80x9d discharge or system of discharges which is blown out from the hollow electrode from which it is at least partly separated by a layer of dielectric material or which is blown out from the walls of its orifice and/or the system of its cavities.
2. A high-pressure discharge or a system of discharges liking up with the discharges of types 1 and 2, and which is generated by dielectric elements of the hollow electrode, will take place by:
c) polarisation and/or the accumulation of the polarisation charge on the walls and edges of the dielectric tube or other dielectric elements of the electrode jet,
d) increasing the density of electromagnetic energy on the transitions conducting material xe2x80x94dielectric (and/or dielectric material of different dielectric constant).
1. A high-pressure discharge or a system of discharges linking up with discharges 1 to 3 outside the hollow electrode in the external environment or the flickering of the plasma generated in discharges 1 to 3.
The rise and permanent generation of the individual discharges or systems of discharges by means of the above facility will take place on fulfilling the following design, working and existence conditions:
1. The rise of the first type of discharge will take place on condition that the middle free electron trajectory in the given working medium under the given pressure remains essentially lower and/or comparable in order with the smallest dimensions of the plasma jet cavity and/or the discharge space outside its orifice and, besides, at the direct-current or low-frequency feeding of the plasma jet under the assumption that the smallest dimension of the cross-section of the electrode cavity be larger than the minimum distance of the negative light from the cathode.
2. The second type of discharge is not limited by the mutual relation of the middle free trajectory of electrons in the given working medium under the given pressure and the smallest dimension of the cavity cross-section of the plasma jet constituting its inner discharge space and/or discharge spaces outside its orifice, just when the so-called xe2x80x9caggravatedxe2x80x9d type of discharge is used inside the hollow electrode, i.e. when the inner discharge space is separated from the conducting part of the electrode cavity by a layer of dielectric material, particularly for the transmission of high-frequency energy.
The blown-out discharge, or the system of discharges from the orifice of the electrode jet can be, even despite its conspicuous species diversity, partly characterised by the temperature of neutral particles in the plasma approximated from the rotary temperature of the OH molecule varying between 300 and 1000 K according to the chosen design variant, the employed working medium and the method of application.
Under low pressures (about 100-103 Pa) in a gaseous or a plasmatic environment these discharges pass continuously into some known kinds of discharges blown out of the plasma jet of hollow geometry (a hollow cathode, etc.).
The method and equipment according to the invention are utilisable in any medium and at any pressure.
I can be utilised:
1. in a targeted way for the activation and modification of the gas, liquid, mixture of gas and liquid or liquid borne dust particles or small objects flowing through the plasma jet
2. for the modification of surfaces of objects
3. for the volume modifications of the treated object
4. for the modification of immersed or dispersed minor objects or compounds situated in the treated objects
5. for the activation of a further working medium consequently affecting the treated objects and/or compounds
6. for the change in the material of the plasma jet or its parts
7. for the plasmochemical synthesis of compounds in the solid, liquid, gaseous, plasmatic or mixed state
8. the employment of the invention is also possible on biological objects (particularly at the high-frequency method of generating the discharge) and other applications.
In manual work with the plasma jet immediate and direct checking of plasmochemical processes and their effects on the treated object is possible, which is excluded or considerably limited when the object is placed in a plasmochemical reactor.